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Permian-Triassic extinction event
For the Cretaceous–Paleogene extinction event, see: K-T extinction Permian–Triassic extinction event was the last and worst of a series of mass extinction events in the Permian period in 252 Ma. This event was Earth's most severe known of all time, with up to 96% of all marine and 70% of terrestrial species becoming extinct. It is the only known mass extinction of . Some 57% of all families and 83% of all genera became extinct. Because so much was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years. Studies in Bear Lake County near showed a quick and dynamic rebound in a marine ecosystem, illustrating the remarkable resiliency of life. Climatic events :(See also: Day 4) The climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an ice age, which began in the Carboniferous. Glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continent's interiors for thirteen million years. In the late Permian period, the drying continued although the temperature cycled between warm and cool cyclesPalaeos: Life Through Deep Time > The Permian Period Accessed 1 April 2013. for another eight million years until the occurrence of the P-T extinction event '' in 252 Ma. ;272.95 – 252 million years ago An unknown global warming phenomena caused an to have occurred as early as the Guadalupian age (272.95 Ma). The triggered a that caused the most severe conditions in Earth's oceanic history, which led to the "The Great Dying" (''P–T extinction) in 252 Ma. There are several developing theories as to what contributed to the anoxic oceans: # , where increases in sea temperatures (and/or drops in sea levels) can trigger a catastrophic positive feedback effect on climate:: first, warming causes a sudden release of from compounds buried in seabeds and seabed permafrost; second, because methane itself is a powerful , temperatures rise further, and the cycle repeats. This runaway process, once started, could be as irreversible as the firing of a gun. #In 2015, evidence and a timeline indicated that the extinction was caused by events in the Large igneous province of the Siberian Traps. The eruptions, which occurred near coal beds and the continental shelf, triggered very large releases of carbon dioxide and methane. Another possible contributor to the extinction may have been from the aftermath of earlier from the in south-western China. #Sea levels in the Permian remained generally low, and near-shore environments were reduced as almost all major landmasses collected into a single continent – Pangaea. Due to the land mass reconfiguration by the end of the period, the reduction of shallow coastal areas that were preferred by many marine organisms, may have contributed to the widespread extinctions of marine species. #The already shallow waters that contained sulfur-reducing organisms, dominated the chemistry of the oceans, and the warming of water temperatures may have caused massive emissions of toxic hydrogen sulfide. See also * Life expansion * Day 4 References Category:Theoretical History Category:Extinction events Category:1.6 Ga–66 mya